Computer systems process information according to a program that includes a sequence of instructions defined by an application program or an operating system. Typically, a program counter provides a series of memory addresses that are used by the processor for fetching instructions stored in the associated memory. In this process, the processor conveys the memory address to the memory over an address bus, and the memory responds over an instruction/data bus with the instruction stored in the addressed memory location. The instructions stored in the memory constitute the program to be executed.
Program development relies heavily on the verification of the instructions stored in memory as well as their corresponding execution. Typically, these debug efforts are supported by instruction tracing tools that generate a listing of executed instructions during the execution of a program.
The increased control and flexibility in the generation of tracing data is particularly important for the embedded processor industry. In the embedded processor industry, specialized on-chip circuitry is often combined with a processor core. However, high performance processors may include features that make it difficult to trace sequential execution of a program. For example, a multi-issue processor may have out-of-order (OOO) dynamic scheduling, deep pipelines, multi-latency pipelines, or support of outstanding load misses.